GB1516885A - Trisequential colour video playback system including means for effecting dropout compensation - Google Patents

Abstract

1516885 Colour television BASF AG 18 Sept 1975 [19 Sept 1974] 38319/75 Heading H4F In a trisequential colour video playback system provided with dropout compensation, a playback channel includes an FM demodulator 6 for elimination of the FM carrier from the FM- modulated video signal recorded in trisequential form, a low-pass filter 7 and a high-pass filter 8 for separation of the high frequency luminance signal portion from the video signal, a detector 12 for detecting a dropout signal occurring in the envelope of the FM modulated video signal, first and second delay devices 9, 10, the outputs from filter 7 and delay devices 9, 10 being fed to a trisequential switch and matrix stage 15 which provides a complete luminance and colour signal in unmodulated form, and a third delay device 11 connected to device 10 and to a switch 13 controlled by detector 12, whereby if a dropout is detected, the switch is operated to connect the output of device 11 to the entrance of the first delay device 9 to replace the output from filter 7. The delay devices each consist of a delay line having a time delay corresponding to a horizontal line scan period. The switch 13 is connected to a second switch 14 which is operated simultaneously with the first switch thereby preventing the passing on of the high frequency luminance signal portion during the occurrence of a dropout. The video system may employ a magnetic tape, a magnetic disc, a piezoelectrical scannable disc or an optically scannable disc. The delay devices may be in the form of bucket brigades or charged coupled devices or peristaltic charged coupled devices. An AM modulator (not shown) feeds AM-modulated signals to devices 9-11, a demodulator being included in matrix stage 15.